1. Field of the Invention
The present invention relates to a semiconductor device including a capacitance element having an MIM (Metal-Insulator-Metal) structure.
2. Description of Related Art
A capacitance element (hereinafter referred to as “MIM capacitance element”) having a structure (MIM structure) obtained by holding an insulating capacitance film between a lower electrode and an upper electrode is known as that constituting a system LSI for radio communication, for example.
FIG. 4 is a schematic sectional view showing the structure of a conventional MIM capacitance element. FIG. 4 partially omits hatching, in order to avoid complication of the illustration.
The MIM capacitance element 101 is provided on a semiconductor device based on a semiconductor substrate (not shown), for example. An interlayer dielectric film 102 is laminated on the semiconductor substrate. A trench 104 is formed on a surface layer portion of the interlayer dielectric film 102. A lower electrode 103 made of Cu (copper) is embedded in the trench 104. The surface of the lower electrode 103 is generally flush with that of the interlayer dielectric film 102. A capacitance film 105 made of SiN (silicon nitride), for example, is formed on the surfaces of the interlayer dielectric film 102 and the lower electrode 103. An upper electrode 106 made of TiN (titanium nitride), for example, is provided on the capacitance film 105. The upper electrode 106 is in the form of a flat plate smaller in size than the lower electrode 103 in plan view, and opposed to the lower electrode 103 through the capacitance film 105.
Another interlayer dielectric film 107 is laminated on the capacitance film 105 and the upper electrode 106. A lower electrode contact plug 108 and an upper electrode contact plug 109 are provided in the interlayer dielectric film 107, to penetrate through the same in the thickness direction respectively. The lower electrode contact plug 108 further penetrates through the capacitance film 105, so that the lower end thereof is connected to the lower electrode 103. The lower end of the upper electrode contact plug 109 is connected to the upper electrode 106.
The capacitance of the MIM capacitance element 101 is proportional to the opposed area of the lower electrode 103 and the upper electrode 106. In an IC chip (semiconductor device) loaded with the MIM capacitance element 101, therefore, reduction of the chip size is hindered due to a large area occupied by the MIM capacitance element.